Package of photographic lightsensitive papers



Nov. 2, 1948.

IN VEN TOR. Stanley fiedericlf William We [ford BY f Z M I ATTORNEY Patented Nov. 2, 1948 UNITED STAT PACKAGE OF PHOTOGRAPHIC LIGHT- SENSITIVE PAPERS Stanley Frederick William Welford, Ilford, England, assignor to Ilford Limited, Ilford, England, a British company .Application February 23, 1945, Serial No. 579,489 In Great Britain March 3, 1944 1 This invention relates to photographic materials and particularly to photographic printing papers and the like. f;

In British Patent No. 550,775 there is described a method of producing a'photographic image wherein a sensitive silver salt paper, coated" on its sensitive surface with a layer of a binder which is insoluble in plain water but soluble in alkali solutions, is exposed with the sensitive surface in contact with a wet negative, and subsequently developed. When a paper so coated is placed in an alkaline developing solution, the alkali therein causes the coating to dissolve. A number of specific binders are described in the-said specification which may be used as the coatings in question. Among these are polyvinyl acid esters, especially of dibasic acids, such as polyvinyl acetate phthalate, esters of polybasic acids, and the compounds formed by condensing a terpene with an a-fi-llllsdliulfil'fid polycarboxylic acid or acid anhydride such as maleic acid anhydride. Among the other materials listed as suitable are the alkyd resins, which are condensation products of polyhydric alcohols as, for

example, glycols, glycerol, sugars and simple derivatives thereof, with polycarboxylic acids, for example citric, maleic, phthalic, succinic and tartaric acids.

Another material which may be so employed is a polymerised methyl methacrylate resin which contains free carboxyl groups, described in U. S. application No. 581,564, filed March 7, 1945, now abandoned, corresponding to British application No. 1,965/44.

It has been found in practice that a difliculty arises in many cases, and particularly in the case where alkyd resin binders are employed, that there is a tendency for the resin, on keeping,lto become less soluble in alkali, thus increasing the time necessary for development, or even rendering the material useless. is accelerated under tropical conditions.

According to the present invention, the

This insolubilisationf 1 Claim. (01. 958) solubilisation of the binder resin, and especially layers, though there may be a water-permeable intermediate gelatin layer. Thus the object of this invention may be achieved by packing the light-sensitive elements in pairs with the resin 2 coatings face to face; Thus a number of sheets of the light-sensitive element may be disposed in a pile, each successive pair having their binder resin surfaces in contact.

Alternatively the rear face (back) of the element may also be provided with a coating of the binder resin in which case the desired result'is achieved whichever way the elements are packed.

However, these methods are not alwaysentirely satisfactory since, although they prevent or re.- tard the insolubilisation of the resin, there-is a tendency for the resin layers to stick together, especially in the case of large packets of the elements, Where the weight of the elements is considerable.

A preferred method, therefore, isto provide the light-sensitive element with a protein backing layer. Thus the element may consist of a paper support coated on one side with a gelatino silver halide emulsion layer supercoated with a resin binder layer which is water-insoluble but alkali.- soluble, and coated on the other side with a plain gelatin layer- Such elementawhen packed face to back, fulfil the object of this invention, i. e. the resin binder layer on the face of oneelement i's in contact only with the protein layerv on -the binder face of the next adjacent element, and

there is very little tendency for the resin layer to become insoluble or for the elements to stick together.

A pack ofthe elements just described is shown in perspective in the accompanying drawing wherein a paper base I is provided on its upper surface with a gelatino silver halide emulsion layer 2. A layer 3 composed of an alkyd resin which is water-insoluble but alkali-soluble is disposed on the emulsion layer. The rear surface of the base is provided with a gelatin layer 4. The latter layer of each successive element in the pack is placed in contact with the resin layer 3 of the next successive element.

According to a further feature of this invention, therefore, a photographic element suitable for printing from wet negatives comprises a support, e. g. of paper, coated on one side with a gelatino silver halide emulsion layer super-coated with a layer of a binder which is water-insoluble but alkali-soluble, and coated on the other side with a protein, e. g. gelatin, layer.

A convenient method of securing the protein backing coat is to apply to the back of the element at 4% aqueous solution of gelatin. Other protein layers may, however, be employed, e. g. casein or zein.

This invention is of primary importance where use of interleaving sheets of wax paper, which also functions, and avoids the difficulties to. which waxed paper tends to give rise under tropical conditions.'

The following examples illustratethe invention:

Example 1 A wet-printing photographic paper consisting of a paper base coated on one side first with a plain gelatin layer, then with a layer of silverhalide gelatin emulsion, and then with a layer the alkyd resin sold under-the. name Paralac :t110 1, ,w a s coated on-theother side with .a solution consisting of:

sl n efore use. dry this coating felt slightly rough to 0 the touch.

Example 2 A wet-printing paper of the character described in Example lwas coated on its rear face with a 4%, aqueous solution of gelatin containing -s llproportions of; chrome alum and formaldehyde as hardening agents.

xamp e 3 Number Name Date 253,354 Eastman Feb. 7, 1882 I 778,740 Chelius Dec. 27, 1904 1,180,415 Nasief; et al Apr. 25, 1916 1,261,748 McCurdy Apr. 2, 1918 1,342,590 Lovejoy June 8, 1920 2,090,016 Young et al. Aug. ;17, 1937 2,173,480 Jung Sept. 19 1939 2,372,935 Challis Apr. 3, 1945 2,373,289 Brown Apr. 10, 1945 2,373,732 Wolfson Apr. 17, 1945 40 2,391,181 Minsk et al. Dec. 18, 1945 OR G ENTS Number 7 Country Date 424,976 Great Britain Mar. 6, 1935 482,204 Great Britain Mar. 24, 1 938 550,775 Great Britain Jan. 25 1943 The products of all these examples showed an improvement over the corresponding products having no coating on the rear surface of the paper base, in that the tendency of the resin coating to become insoluble in alkali was much reduced. Then edu n E ple .l andzl t Preferably packed face to back and thus packed show a much reduced tendency to sticking, while those of Example 3 may be packed either face to back or face to face.

What icla m i A-package of light-sensitive elements each elementcomprising a, paper support carrying on one side thereof g gelatino silver halide emulsion layer and a superimposed layer of an alkyd resin which is water insoluble but alkali-soluble and carrying on the other side thereof a layer of gelatin, the said elements being packed in the package face to ibaq STANLEY FREDERICK WILLIAM WELFORD.

REFERENCES CITED T e iq lowins ref e ces are o e o d n. t e 

